Double-hung, tilt-out type windows have become increasingly popular. Much of this popularity is due to the tilt-out feature which allows both inside and outside surfaces of the window to be cleaned from the inside.
Tilt-out windows have been equipped with locking slide blocks such as the one disclosed in U.S. Pat. No. 4,610,108 to Marshik. Marshik discloses a double-hung window having a frame with a set of parallel jamb channels on opposite sides of the frame. Within each jamb channel is a slidably mounted locking block. A spring counter-balance mechanism is attached to a headplate on each block. A pivot extends from proximate the lower end of opposite sides of a sash into a locking cam housed within the block. The pivots allow the sash, which holds a window pane, to be rotated or tilted toward the inside. As the pivots rotate, the cam forces serrated ends of a spring into opposite sides of the jamb channel to prevent the counter-balance spring from pulling up the blocks and sash while cleaning.
U.S. Pat. No. 4,813,180 to Scalzi discloses another locking sliding block for double-hung windows. Like the '108 patent, a locking block is slidably mounted within jamb channels and a pivot extends from opposite sides of the sash into a pivot button or cam in each locking block. Unlike the '108 patent, however, the pivot has a slot which engages a retaining ridge in the pivot button. This is intended to prevent dislocation of the pivots during transport and installation of the window due to deflection or bowing of the frame away from the sash. The locking block disclosed by Scalzi, although allowing the sash to pivot inside for easy cleaning of the window pane, does not allow the window to be conveniently removed from the inside.